Redundancy and tautology are undesirable, and a sign of less than careful writing.
This coinage has often provoked the accusation that nothing is really being asserted in the argument for natural selection: since fitness can only be defined by survival the phrase is a tautology .
The past, in effect, is a tautology ; it is true by virtue of its logical form alone.
Some authors treated the quantity theory as a matter of causal relation and explanation, often differing as to the content and direction of explanation, whereas others saw it as a truism, identity or tautology .
Note the tautology in the first sentence, the feeble attempt at punnery.
The footpath outside the front of our house is flanked on both sides (is that tautology ?) with low bushes.
Julian concurred that evenings set aside for communication with ‘dead angels’ (I'm sure there's some tautology in there) were right up his street and he couldn't believe he'd missed it.
But really, spinning out some kind of clever model to illustrate that idea is unnecessary tautology : I can say it in just a few simple words.
It is conceivable that the key to truth lies in tautology and redundancy.
It doesn't affect the validity of the statement, so you can include it without destroying your tautology .